Transition from One- to Two-Dimensional Growth of Cu on Pd(110) Promoted by Cross-Exchange Migration

A transition from one- to two-dimensional structures is observed in the growth of Cu islands on Pd(110). When Cu is deposited at substrate temperatures below 300 K, the adatoms move along the easy [1 0] direction forming 1D Cu chains. At higher temperatures transverse diffusion of adatoms is activated and 2D islands start to grow. Migration barriers are found to be (0.51 ± 0.05) eV and (0.75 ± 0.07) eV along and across the [1 0] directions, respectively. In the two-component driven diffusion regime, the shape of the 2D Cu islands is determined by the energy difference of the two orthogonal diffusion barriers.